Secondary Clutch/8DN made easy

[stingray719]

A lot of confusion I am seeing in private messages so I thought I would try to clarify here. Don't get me wrong I don't mind private messages but more people get the info this way.

1. Secondary clutch shims.
a. Shims required for 8DN belt. This is different from other shims like helix shims or center shims.

On the back of the secondary clutch are 3 small bolts. (first pic below one bolt removed) They push in and hold the secondary apart to adjust belt deflection in the closed or stopped position (that is in simple terms the belt slack or tightness). Yes I know why so archaic of a method for belt deflection. Anyways those of you that rode Yamaha very long know these bolts get beat up and shorten and you have to replace them when the deflection changes usually noticed by belt squealing and sled trying to creep at idle. So new bolts if the belt rides too high over the sheave, and add washers if the belt rides too low.

So when you install an 8DN belt you need to check deflection. When the ribs just stick above the sheave you are correct. This in my opinion is not an exact science so a little leeway is ok here as long as it is close (disclaimer: close is relative term though) The pic below is close to what I consider proper belt deflection, maybe a hair high. (not going to adjust it a hair for this pic...lol)

So when you add an 8DN belt you may need to add another washer to this bolt to space apart the sheaves for proper belt deflection and getting the 8DN to the deflection shown above. Here is a bolt and everyday garden variety of washer added for most 8DN installs (NOTE: some 8DN go on and do not need any adjustment) Obviously same size washer set on all 3 bolts. You can also have machining done instead of washer but it is not necessary.

You still have secondary off, wrap belt around sheave and check deflection. Reinstall when correct.

NOTE!!!!!!!!!!! Belts have a lot of difference even when new, check deflection when changing belts even the same size belts.








2. Helix shims
a. Helix shims are for reducing the secondary coil spring bind. The best way is to have your secondary or helix machined to get rid of coil bind but if you choose instead to shim the helix (this is usually used to test whether coil bind is affecting you to decide if you wish to machine your parts) this is how. NOTE: this is not the recommended long term solution to coil bind.

Remove Helix and put 3 washers all the same size on the studs as shown below and bolt helix back on. Test and decide if you wish to machine your secondary or helix and THEN REMOVE WASHERS as this is not the recommended way and put here only to remove confusion about the different secondary shims being discussed.

 

[Studroes144]

Are these viper clutches?

 

[tapex_07]

Nice write up

 

[stingray719]

Are these viper clutches?

Barry what part on a Mountain Max secondary is different than a Viper in these pics?

 

[Studroes144]

N

Barry what part on a Mountain Max secondary is different than a Viper in these pics?

Never looked at a mountain max secondary..but I don't imagine it's the terrible amount of belt dust

 

[stingray719]

N


Never looked at a mountain max secondary..but I don't imagine it's the terrible amount of belt dust

Heh, not belt dust...that old secondary is a throw away that was sitting under the grinder.....LOL!

 

[weasel33]

Thanks stingray, the way you explain and show us with pictures really help us guys that don't know a lot about clutching and how it works.

 

[sxr70001]

I used some of those old beat up clutch bolts from my clutching box on my viper. That way I didn't have to use so many washers.

Just make sure you check them with a caliper first to make sure they wore down evenly.

 

[yamadoo]

Thanks well done!!

 

[cannondale27]

Thanks Stingray. I will put this in the Fact thread under clutching.

 

[TD Max]

From what I have read, most end up just taking out the bolts because when you add all the shims required to get the deflection set the bolts aren't doing anything. This means you have no way to adjust deflection further as the belt wears assuming you can get it set right in the first place.

I believe Kerrdog could not get his deflection set to his satisfaction without having his secondary machined.

 

[wavemaster]

Great Job! This is the stuff that really makes this forum the best.

Question?

Following the "clutching on the cheap" I purchased a 40-46 Helix from Ulmer as well as the new belt/spring/weights that I plan to install after the sleds initial break-in.

Do you know if the 40-46 helix will have the same spring bind issues seen on the stock helix?

 

[Studroes144]

40-46 helix or 46-40?

 

[stingray719]

From what I have read, most end up just taking out the bolts because when you add all the shims required to get the deflection set the bolts aren't doing anything. This means you have no way to adjust deflection further as the belt wears assuming you can get it set right in the first place.

I believe Kerrdog could not get his deflection set to his satisfaction without having his secondary machined.

Lots of "I heard" going around I am afraid. The 8DN and for that matter most belts are built to some pretty loose standards and you may find some rather large variance. As I said before one of our Viper needed extra washers and one did not. I would like anybody that ran out of adjustment with a healthy belt within accepted belt tolerance to please post though as I would really like to know if that can become an issue. I tried all 6 of my 8DN for fit so I would know what I could use and although they varied greatly none of them could not be set correctly. But, as I said above lets see if that might be the case and if so was it one clutch built out of tolerance or will most do it.

 

[stingray719]

Great Job! This is the stuff that really makes this forum the best.

Question?

Following the "clutching on the cheap" I purchased a 40-46 Helix from Ulmer as well as the new belt/spring/weights that I plan to install after the sleds initial break-in.

Do you know if the 40-46 helix will have the same spring bind issues seen on the stock helix?

Good question, are Ulmer helix relief cut in the spring pocket for coil bind? Allen?